Due to the ever-increasing popularity and accessibility of the Internet as a medium of communication, the number of business transactions conducted using the Internet is also increasing, as are the numbers of buyers and sellers participating in electronic marketplaces providing a forum for these transactions. The majority of electronic commerce (“e-commerce”) transactions occur when a buyer determines a need for a product, identifies a seller that provides that product, and accesses the seller's web site to arrange a purchase of the product. If the buyer does not have a preferred seller or if the buyer is purchasing the product for the first time, the buyer will often perform a search for a number of sellers that offer the product and then access numerous seller web sites to determine which seller offers certain desired product features at the best price and under the best terms for the buyer. The matching phase of e-commerce transactions (matching the buyer with a particular seller) is often inefficient because of the large amount of searching involved in finding a product and because once a particular product is found, the various offerings of that product by different sellers may not be easily compared. After identifying a suitable seller, a buyer may contact the seller and negotiate a contract for the sale of certain products. Product data specifying the products that are the subject of the contract may be included in the contract. Such data, when recorded in an electronic or other copy of the contract kept by the buyer, the seller, or both may be susceptible to being changed without there being any way to easily detect the changes. As a result, it may be difficult to ascertain with certainty the original terms of the contract.